A bank loaned out 19,000$, part of it at the rate of 8% per year and the rest at 18% per year. If the interest received in one year totaled $2000, how much was loaned at 8%

Use stokes' theorem to evaluate c f · dr where c is oriented counterclockwise as viewed from above. f(x, y, z) = xyi + 5zj + 7yk, c is the curve of intersection of the plane x + z = 8 and the cylinder x2 + y2 = 81.